The term “USGA green” is often used to identify a green that was built according to the USGA Recommendations for a Method of Putting Green Construction. Unfortunately, this term is often misused to describe any putting green built with a sand-based rootzone. While all greens that meet USGA construction recommendations are in fact built out of a sand-based rootzone, it is important to recognize that not all sand-based greens are “USGA greens.” This article will point out some key characteristics of a true USGA green.
- A USGA green is built with 12 inches (+/- 1 inch) of sand-based rootzone mix above a minimum 4-inch layer of gravel over a network of drainage pipes. USGA recommendations also include specific guidelines for the sand and gravel used in construction.
- The sand and gravel specifications have intentional variability built in, and are included so that the rootzone mix has characteristics important for putting green performance. These characteristics include infiltration rate, moisture retention, aeration porosity, and the propensity to compact appropriately. Just because a sand-based rootzone mix is used does not mean that a green was built according to USGA recommendations, or that it will perform well. The details of the mix and gravel really do matter.
- The depth of the rootzone mix also matters. USGA recommendations call for a uniform 12-inch rootzone depth (+/- 1 inch) throughout the putting green. The 2018 Tips for Success document included a discussion about how some courses have successfully built putting greens with a variable depth rootzone, even though this method does not conform to USGA recommendations. It is important to understand that this option calls for more rootzone material in low areas of the greens (> 13 inches), and less mix in the higher areas (< 11 inches). Oftentimes, when last-minute changes are made to putting green surface contours the opposite occurs and less mix ends up in the lows and more mix is placed on higher areas. This should be avoided at all costs, otherwise the lows can stay wet and the highs will dry out even faster.
- The drain lines in the floor of a USGA green should be no more than 15 feet apart and should extend all the way to the putting green cavity wall. Drainage pipe should also be placed along the cavity wall in any low areas or drainage exit points. This feature is often called a “smile drain.” The drainage pipes should have a minimum diameter of 4 inches and the trenches should be at least 6 inches wide and 8 inches deep to allow for gravel to surround the pipes. Flat pipes may also be used and their placement should follow all the other recommendations.
Golf courses have been building putting greens according to USGA recommendations for decades with great success. The recent surge in renovation work should put many courses in a good situation for years to come, but when it comes to putting green construction it is important to dive into the details. Recognize that building a sand-based putting green can be far different than a “USGA green” and performance will often reflect that! If you are considering a putting green renovation project or new construction, contact your regional USGA agronomist to help guide you through the materials selection and construction process.
Central Region Agronomists:
Zach Nicoludis, regional director – znicoludis@usga.org
Paul Jacobs, agronomist – pjacobs@usga.org